1. Field of the Invention
The invention relates to an axial piston engine which, while affording a stable construction, provides for a multitooth coupling facilitating a fluid flow penetration and/or mechanical penetration between opposite sides of the multitooth coupling.
An axial piston engine of said type is described in DE 32 22 210 A1.
2. Discussion of the Prior Art
In axial piston engines it is known to utilize the housing interior as an intermediate collecting container for leakage fluid. In the operating mode of the axial piston engine, in the housing interior a specific amount of leakage oil collects, which is under low pressure and flows off through a discharge gap or discharge channel to a tank. The leakage fluid situated in the housing interior may be used to lubricate moving parts of the axial piston engine. It is moreover advantageous when the leakage fluid is present as a film between the seating surfaces of parts which are not movable relative to one another, thereby preventing or at least reducing contact corrosion and abrasion resulting from vibrations. It is further advantageous when the hydraulic fluid may travel with as little hindrance as possible to the desired lubricating points. This is not guaranteed when in the housing interior there is a barrier preventing a desired feed of the fluid to the lubricating point. Such a barrier is formed by a multitooth coupling between two parts of the axial piston engine in the housing interior of the latter. The purpose of a multitooth coupling is to connect two parts rigidly to one another, e.g. prevent them from rotating relative to one another. In the axial piston engine of the initially indicated type, such a multitooth coupling may be provided between a driving shaft and a cylinder drum mounted thereon. Since a multitooth coupling is to transmit considerable coupling forces, the aim is to fashion the mutually adjacent surfaces of the multitooth coupling not only in the region of the tooth flanks and the tooth spaces in such a way that they fit substantially tightly against one another. As a result, the multitooth coupling forms a liquid barrier, which prevents or at least reduces the access of the hydraulic fluid to both sides of the multitooth coupling.
From the previously mentioned DE 32 22 210 A1 it is also known for a support ring, which is mounted on the driving shaft and has a spherical segment-shaped support surface for a retaining plate for holding back sliding pads, to be positioned in the operating position by means of axially disposed thrust pins lying opposite one another on the periphery of the driving shaft, wherein the thrust pins are mounted in a sliding displaceable manner in bores, which extend in the region of the multitooth coupling between the support ring at the one side of the multitooth coupling and a thrust ring at the other side of the multitooth coupling. The thrust ring is biased by a pressure spring towards the thrust pins and towards the support ring, wherein the end of the pressure spring remote from the thrust ring biases the cylinder drum elastically towards a cam disk. In said development too, the multitooth coupling forms a barrier preventing the fluid from flowing from the one side of the multitooth coupling to the other. In the known development this is particularly problematical because the fluid is prevented from flowing into an annular clearance zone between the driving shaft and the cylinder drum. A rolling-contact bearing disposed in the region of a cam disk and provided for mounting the driving shaft rotatably on the relevant housing wall is therefore cut off from being intensively flushed, lubricated and cooled by the hydraulic fluid.
Furthermore, the gearing is weakened if the bores for the thrust pins extend right through the middle of the teeth or if a tooth is left out in the region of a thrust pin. DE 198 28 429 A1 describes an axial piston engine having a return apparatus comprising thrust pins, which is similar to the previously described return apparatus. In said previously known development, three thrust pins arranged so as to be distributed over the periphery are displaceably mounted in each case in a first through-channel, which is disposed in the root region of a missing tooth of the cylinder drum. In said non-generic development, the missing teeth form two through-channels for the fluid. In said development too, the stability and/or strength of the toothed ring coupling is impaired because of the missing teeth.
The underlying object of the invention is to develop an axial piston engine of the initially indicated type in such a way that, while simultaneously guaranteeing a stable construction, the multitooth coupling enables a flow penetration and/or a mechanical penetration from one side of the multitooth coupling to the other.
Said object is achieved by the features as described herein. Advantageous developments of the invention are described in the sub-claims.
In the construction according to the invention a flow of fluid through the through-channel from one side of the multitooth coupling to the other is possible so that in the operating mode the fluid reaches both sides of the multitooth coupling and the lubrication in said regions is guaranteed. Since the at least one through-channel according to the invention is disposed in a tooth tip surface and/or in an opposing tooth space bottom surface, it is situated in a region which is insensitive to weakening and the flanks of the teeth and/or tooth spaces are unimpaired.
As the main load zone of the multitooth coupling is situated in the region of the flanks, the construction according to the invention leads neither to a substantial weakening of the cross section of the teeth nor to a reduction of the compressive load per unit area. The stability and endurance of the multitooth coupling are therefore maintained despite the presence of one or more through-channels arranged so as to be distributed over the periphery.
For fluidic reasons it is advantageous to dispose a plurality of through-channels preferably so that they are distributed uniformly over the periphery of the gearing. It is also possible to dispose the through-channel only in one of the mutually opposing tooth tip surface and tooth space bottom surface or in a mutually opposing manner in both surfaces. The latter leads to a common through-channel of enlarged cross section.
The cross-sectional shape of the at least one through-channel may differ and be adapted to constructional conditions. A rounded or half-round or U-shaped cross-sectional shape is advantageous for avoiding a notch effect. The cross-sectional shape may however also be polygonal or hollow wedge-shaped, this being advantageous for reasons of manufacture and for additional reasons explained further below.
The at least one through-channel according to the invention may however also be used to receive a pin as part of the axial piston engine, e.g. a previously described thrust pin extending between two axially movable components disposed on either side of the multitooth coupling, e.g. between a pressure spring and a support ring for a return device. The thrust pin penetrates the through-channel and may, for example, be guided slidingly therein with slight motional clearance. In said case, the through-channel is used not to create a flow connection between both sides of the multitooth coupling but to enable a mechanical connection extending through the through-channel and, indeed, likewise without substantially impairing the stability of the gearing.
In said case, the pin may be slideably guided in the through-channel with slight motional clearance, so that a fluid penetration is not provided. When the at least one through-channel is designed with a cross section sufficiently larger than the pin, the construction according to the invention may form a passage both for the mechanical connection and for the fluid.
The through-channel is open towards the tooth tip surface and/or tooth space bottom surface. The advantage of said construction is that the at least one through-channel may be manufactured easily and inexpensively in the form of a groove, e.g. by a cutting operation using a slotting tool, a broaching tool, a roller-type hammering tool or a milling tool, especially with inclusion of the profile in the milling cutter geometry.